1. Field of the Invention
The present invention relates generally to door hinges, and more specifically to self-closing hinges equipped with springs. While the invented hinge may benefit many self-closing door applications, preferred embodiments are especially beneficial for commercial, walk-in freezer doors.
2. Related Art
Many door hinges have been developed that comprise a self-closing feature for urging a door toward a closed position. This feature may be included on doors for reasons of safety, privacy, convenience, and/or energy-savings, for example, in hospitals, rest homes, public restrooms, and walk-in and other freezers. Several self-closing hinges have been patented in the past, including Winter (U.S. Pat. No. 1,108,298); Benham (U.S. Pat. No. 3,107,758); Berkowitz (U.S. Pat. No. 3,748,688, assignee Kason Hardware Corporation); Kaiser (U.S. Pat. No. 3,975,794, assignee Vollrath Refrigeration Company); and Loikitz (U.S. Pat. No. 4,030,161, assignee Buildex Incorporated). These patents are discussed in more detail later in this document.
Means by which door hinges are made to include a self-closing feature typically fall within two categories, that is, 1) a cam/slanted surface that tends to swing the door toward a closed position when gravity pulls the door and its hinge portion downward relative to the stationary hinge portion and surrounding stationary structure; and 2) a spring-bias that urges the door closed. The first is frequently called “a gravity hinge” and the latter is frequently called “a spring hinge.”
In hinges that utilize gravity to assist/urge the door into the closed position, a helical-cut lift-cam surface is typically included in the hinge, which lift-cam surface causes the door to rise slightly as it is swung open by a user. When the door is released, gravity causes the door to swing closed, as the hinge portion connected to the door, in effect, slides down the lift-cam surface as it rotates.
In hinges that utilize spring-bias to assist/urge the door into the closed position, a spring is typically included in the hinge. The spring is positioned and adapted so that the door swinging open tends to move the spring into a position of potential energy that, when the door is released, works to close the door.
Walk-in freezer doors often are equipped with self-closing hinges that comprise both gravity-assist and spring-bias features. Hinges with a cam-based gravity-assist feature and the resulting raising of the door during opening, can be especially beneficial in a freezer because it helps keep the freezer door, and any seals on the doors bottom edge, from scraping against the floor. In a walk-in freezer, wherein it is desirable to not have a raised threshold in the doorway, the door and its bottom seal will tend to be at, or very close to, the level of the floor. Repeated opening and closing of the door, without raising the door slightly, would quickly damage the sealing capability of the door, and the cam-based gravity-assist feature helps prevent this.
Adding a spring-assist feature to the freezer door hinge supplements the self-closing feature, to increase the likelihood that the freezer door will reliably close. Walk-in freezer doors are insulated with foam and are surprisingly light for their large size, which poses the problem of the door not latching properly. The gravity force acting on a lightweight door (to close it with the aid of its gravity-hinges) is not as great as it would be on a heavy door, and, since a freezer is, in effect, an airtight room, air rushes to escape the freezer as the door nears the fully-closed position. This sudden rush of air can slow the door down so much that it does not have enough momentum to latch on its own. For this reason, springs are typically incorporated into the door hinges to assist the cam-based gravity-assist in closing the door. In currently-available freezer hinges, these springs are presently positioned either above or below the cams, so that, when the cams “separate” (slanted surfaces sliding relative to each other, during rotation typically of one of the cams, so that the over-all length of the cam system structure increases) as the door opens, the spring compresses so that the spring's force tends to force the cams to move “back together” to close the door (slanted surfaces sliding relative to each other during rotation of said one of the cams in the opposite direction so that the over-all length of the cam system structure decreases).
Prior art hinges place the spring entirely above or below the cam, which extends the overall height of the hinge by a substantial amount, for example, 2 to 3 inches compared to some hinge embodiments invented by the present inventors. The extra height in present hinge designs usually takes the form of a sleeve for the spring that moves like a plunger as the door opens and closes (for example, see the hinge available from Kason Industries, Inc., Shenandoah, Ga., USA, model 1248, shown in FIG. 1A). The Kason hinge is not adapted for convenient removal or adjustment of the spring, but it does have lift-off capability (allowing the door and blade to be lifted off the hinge housing without removing any hardware). The hinge available from Component Hardware Group, Inc., Lakewood, N.J., USA, (Components model W-62, shown in FIG. 1B) has a plunging bolt, but it is enclosed in a stationary cylinder above the blade. The Component hinge has an adjustable, removable spring, but it has the disadvantages that the retaining nut is clearly visible and that the hinge is not a lift-off design. The Kason and Component hinges are discussed in more detail below.
The first introduction of the spring to a gravity-driven, self-closing door that is known to the inventors is seen in U.S. Pat. No. 1,108,298 by Winter, who points out that spring assistance is necessary in applications where the weight of the door is insufficient. U.S. Pat. No. 3,107,758 by Benham disclosed a hinge wherein the spring is placed above the cams and the door may not be removed by simply lifting it off the hinges. The Benham hinge, however, is not designed for use on commercial freezer doors and requires built-in receiving brackets.
A hinge tailored to freezer doors is seen in U.S. Pat. No. 3,748,688 by Berkowitz. The Berkowitz design is still in use by Kason Industries and Berkowitz patent number can be seen printed on the blade of the Kason model #1248 hinge. In Berkowitz is seen the now-familiar helical cam pair, noncircular lifting pin or pushrod, and right- or left-hand operation. Note also that this Berkowitz hinge is a lift-off design. Missing from the Berkowitz hinge is a spring to assist in closing; the inventors believe that the Berkowitz hinge lacks the additional closing force necessary to properly latch a light door when the door is allowed to self-close.
Following Berkowitz were others working to refine freezer door hinges. U.S. Pat. No. 3,975,794, by Kaiser, places the spring above the cams again and simply adds torsion to compression with regard to the spring when the door is opened. In this case, the spring life is shortened by the torsional loading. The additional force provided by the torsional loading, although likely to be unnecessary in modem door hinges, could easily be matched by the capability of embodiments of the instant invention to allow springs of larger wire diameter and higher spring rates. Finkelstien (U.S. Pat. No. 4,991,259) also places a spring at the top of the hinge in a protruding spring shell. Neither Kaiser nor Finkelstien is a lift-off hinge.
U.S. Pat. No. 4,030,161 by Loikitz appears to be the design presently used by Component Hardware Group, although there is no patent number printed on the Component brand W-62 hinge (shown in FIG. 1B). The spring used in the Loikitz patent is believed by the inventors to be too small to contribute sufficiently to the closing force. Modern Component brand hinges use a much larger spring than is shown in Loikitz and that is encased in a sleeve that protrudes from the top of the blade (as seen in FIG. 1B). This protruding spring sleeve, as mentioned previously, introduces an aesthetics problem. In addition, the Loikitz design and the Component brand hinge do not result in a lift-off hinge and do not conceal the large nut attached to the threaded bolt that passes through the entire mechanism.
There exist many prior works involving spring and cam arrangements designed to keep a door from rising during opening. Contrary to such teachings to eliminate the rise, a rise is actually preferred in freezer doors, as it prolongs the life of the lower door seal by preventing sliding contact with the floor.
Still, even in view of the many prior art hinges, the inventors believe that there is a need for a more compact and aesthetically-pleasing door hinge that comprises a gravity-assist feature and preferably also a spring-assist feature. The inventors believe that there is still a need for a door hinge that may be used with or without a spring, wherein, when in use with a spring, the spring is adjustable even through the preferred hinge is a reversible, lift-off hinge (spring adjustment and lift-off capability being mutually-exclusive in prior art hinges). The preferred embodiments of the invention meet these needs.